a recent infectious illness such as the flu, mononucleosis or hepatitis

thyroid problems

hormonal disturbances, such as menopause

diabetes

poor diet or lack of exercise

lack of sunlight (known as seasonal affective disorder, which occurs during the dark fall and winter months)

Everyone feels “down” sometimes. It’s normal to grieve over the death of a loved one, a serious illness, the loss of a job or even retirement. But when does normal sadness turn to depression, and what can be done about it?

Contrary to what many people believe, depression is not a natural consequence of growing old or a sign of personal weakness. Rather, depression is a medical illness—and a highly treatable one. An imbalance in brain chemicals known as neurotransmitters appears to be a key factor in the development of depression. In some people, the level of certain chemicals may be too low or too high, predisposing them to the illness. A stressful event may trigger depression in these susceptible individuals.

People are also more susceptible to depression at particular stages in their lives: adolescence, middle age and after retirement. In fact, people over 65 make up a disproportionate number of suicides.

Recognizing depression

Although symptoms vary, the most common is loss of interest in normal activities. This leads to feelings of emptiness, apathy and withdrawal. A person may be unable to concentrate, have problems sleeping, lose his or her appetite or have other physical complaints.

A thorough evaluation by a doctor is the first step in diagnosing depression. It’s essential because depression can be a complication of another medical problem (see “Doctors look for these culprits”). Your doctor may treat your depression or refer you to a psychiatrist.

If depression is diagnosed, the treatment can relieve symptoms in four of five cases, usually within a few weeks. Standard treatments for depression include psychotherapy, antidepressant medication or a combination of both.

Learning how to cope

Psychotherapy helps patients manage their thoughts, feelings and behaviors. The process helps people replace negative thoughts with positive ones and resolve their differences with others. It also teaches skills for living a more productive and satisfying life.

Antidepressant medications, which help to restore the natural balance of brain chemicals, are often enough to relieve depression. These drugs are nonaddictive, and many newer agents have fewer side effects than earlier drugs. Antidepressants take effect gradually, so it can take a few weeks before patients notice that their medication is working.

Unfortunately, most people who are depressed don’t seek help—because they don’t recognize that they need it or they perceive depression as a personal failing and are embarrassed to admit they need help.

If you’re experiencing symptoms of depression, consult your doctor or call the hospital for a referral. Remember: Most people with depression recover; prompt treatment speeds the process.